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Scubadoc's Diving Medicine Online
Comprehensive information about diving and undersea medicine for the non-medical diver, the non-diving physician and the specialist. 
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GLOSSARY
of Diving Medical Terms

A || B || C || D || E || F || G || H || I || J || K || L || M ||
N || O || P || Q || R || S || T || U || V || W || X || Y || Z


A

Abdominal hernia - a weakness of the abdominal wall through which the intestines or other intraabdominal contents protrude. Dangerous to a diver if a loop of air-containing intestine is trapped outside the abdomen.
 http://www.scuba-doc.com/giprbs.html

actual bottom time (ACT) - Total elapsed time in minutes from leaving the surface until ascent is initiated.

Acute Blood loss Anemia - Anemia brought on by hemorrhage. An indication for the use of hyperbaric oxygenation.
 http://www.scuba-doc.com/hbo.html

AGE - Abbreviation for arterial gas embolism
 http://www.scuba-doc.com/ageprbs.html

air - a gas mixture containing 21% oxygen, 78% nitrogen, and 1% other gases (mainly argon); compressed air is used for recreational scuba diving. 
 http://www.scuba-doc.com/gasesprbs.html

air compressor - a machine that compresses or pressurizes air; for scuba purposes, air is compressed from the atmospheric level (14.7 psi at sea level) to the capacity of the tank, usually between 2500-3000 psi.

air embolism - see arterial gas embolism
 http://www.scuba-doc.com/ageprbs.html

air pressure - the force per unit area exerted by the weight of air; at sea level the air pressure is 14.7 psi. Air pressure decreases with altitude.   http://www.scuba-doc.com/gasesprbs.html

Alcohol - mood and attitude altering chemical that is a substance often abused by individuals. It is exceedingly dangerous underwater due to it's ability to alter the decision making processes. http://www.scuba-doc.com/alch.htm

algorithm - a set of equations incorporated into diving computers in order to compute nitrogen uptake and elimination from changes in depth and elapsed time.

Alternobaric Vertigo - dizziness brought on by the inequality of pressures in the inner ear. http://www.scuba-doc.com/vert.htm

Altitude Sickness - an illness brought on by the sudden reduction in pressure of ascent to altitude.
 http://www.scuba-doc.com/flyafdv.html

alveolus - air sac at the terminus of a bronchus where oxygen and carbon dioxide transfer occurs.
 http://www.scuba-doc.com/pulprbs.html

Anemia - any reduction in the oxygen carrying capacity of the red blood cells.  http://www.scuba-doc.com/hematology.htm

Anticoagulants - Medications that reduce the clotting ability of the blood. Particularly dangerous to divers due to barotrauma of air-filled body cavities.  http://www.scuba-doc.com/hematology.htm

ambient pressure - the surrounding pressure; on land, comes from the weight of the atmosphere (see air pressure); at depth, comes from the weight of the water plus the weight of the atmosphere. http://www.scuba-doc.com/gasesprbs.html

argon - an inert gas that makes up less than one percent of air. 
 http://www.scuba-doc.com/gasesprbs.html

Arrhythmias - irregularities in the rhythm and rate of the heart, particularly dangerous to divers due to the underwater environment.  http://www.scuba-doc.com/hrtprb.html

arterial gas embolism - the condition characterized by bubble(s) of air from a ruptured lung segment under pressure; the bubbles enter the pulmonary circulation and travel to the arterial circulation, where they may cause a stroke. (AGE or CAGE).
 http://www.scuba-doc.com/ageprbs.html

asthma - a common condition manifested by narrowing of air passages within the lungs (the bronchi); one reason for the narrowing is excess mucous in the airways.
 http://www.scuba-doc.com/asthma.htm

ata - atmosphere absolute; 1 ata is the atmospheric pressure at sea level; is measured with a barometer.
  http://www.scuba-doc.com/gasesprbs.html

atmosphere - the blanket of air surrounding the earth, from sea level to outer space. Also, a unit of pressure; "one atmosphere" is pressure of the atmosphere at sea level, i.e., 760 mm Hg. Two atmospheres is twice this pressure, 1520 mm Hg, etc. Abbreviated atm.
  http://www.scuba-doc.com/gasesprbs.html

atmospheric pressure - pressure of the atmosphere at a given altitude or location.
 http://www.scuba-doc.com/gasesprbs.html


B

Barodontalgia - pain and discomfort caused by volume and pressure changes in carous teeth.
 http://www.scuba-doc.com/dentprbs.html

barometric pressure - same as atmospheric pressure.
  http://www.scuba-doc.com/gasesprbs.html

barotrauma - any disease or injury due to unequal pressures between a space inside the body and the ambient pressure, or between two spaces within the body; examples include arterial gas embolism, pneumomediastinum, and pneumothorax, eye, middle ear and sinuses and the lung.
 http://www.scuba-doc.com/gasesprbs.html

BC - see buoyancy compensator.

bends - a form of decompression sickness caused by dissolved nitrogen leaving the tissues too quickly on ascent; is manifested by pain, usually in the limbs and joints; "the bends" is sometimes used to signify any manifestation of decompression sickness.
 http://www.scuba-doc.com/dcsprbs.html

bleb - an abnormal pocket of air in the lungs, usually under the lining of a lung, that can rupture with ascent and lead to barotrauma.
 http://www.scuba-doc.com/pulprbs.html

Body Mass Calculation - http://www.scuba-doc.com/Nutrition.htm#Body Mass

bottom time - variable definition; in square wave diving, the time between descending below the surface to the beginning of ascent. In multi-level diving, the time between descending below the surface and beginning the safety stop. (Other definitions may apply depending on the specific type of diving.)

Bowel Disease, Inflammatory - Inflammations of the intestine, including Crohn's disease and chronic ulcerative colitis. Some forms have complications that are adverse to diving.
 http://www.scuba-doc.com/giprbs.html

Boyle's law - at a fixed temperature and for a fixed mass of gas, pressure times volume is a constant value.
  http://www.scuba-doc.com/gasesprbs.html

breath-hold diving - diving without life support apparatus, while holding one's breath.
 http://www.scuba-doc.com/gasesprbs.html

bubble - a collection of air or gas surrounded by a permeable membrane through which gases can enter or exit.
 http://www.scuba-doc.com/dcsprbs.html

bulla - similar to bleb; an abnormal pocket of air or fluid; sometimes found in the lungs of patients with emphysema.
 http://www.scuba-doc.com/pulprbs.html

buoyancy - tendency of object to float or sink when placed in a liquid; objects that float are positively buoyant, those that sink are negatively buoyant and those that stay where placed are neutrally buoyant. Buoyancy control is a very important factor in diving safely.
  http://www.scuba-doc.com/gasesprbs.html

buoyancy compensator - an inflatable vest worn by the diver that can be automatically or orally inflated to help control buoyancy; abbreviated BC.


C

CAGE - Abbreviation for cerebral arterial gas embolism (See arterial gas embolism)
 http://www.scuba-doc.com/ageprbs.html

carbon dioxide - CO2; an odorless, tasteless gas that is a byproduct of metabolism; is excreted by the lungs in exhaled air. Important in the control of respiration.
 http://www.scuba-doc.com/gasesprbs.html

CO2 Retention - frequent cause of CO2 toxicity, usually from skip breathing.
 http://www.scuba-doc.com/gasesprbs.html

carbon dioxide toxicity - problems resulting from buildup of CO2 in the blood; they may range from headache and shortness of breath, all the way to sudden blackout.
 http://www.scuba-doc.com/gasesprbs.html

carbon monoxide - CO; odorless, tasteless, highly poisonous gas given off by incomplete combustion of hydrocarbon fuels.
 http://www.scuba-doc.com/gasesprbs.html

carbon monoxide toxicity - illness from inhaling excess CO; problems may range from headache to unconsciousness and death.
 http://www.scuba-doc.com/gasesprbs.html

Charles' Law - at a constant volume, the pressure of a gas varies directly with absolute temperature.

At a constant pressure the volume of a mass of gas is
proportional to the absolute temperature.

V1/T1=V2/T2
or
T x P = V
http://www.scuba-doc.com/gasesprbs.html
 

chokes - a form of decompression sickness caused by enough bubbles entering the lungs to interfere with gas exchange; manifested by shortness of breath and can be fatal.
 http://www.scuba-doc.com/dcsprbs.html

Chronic Adverse Effects, Bone - dysbaric osteonecrosis; bone damage done by nitrogen bubbles in the bones.
 http://www.scuba-doc.com/bone.htm

Chronic Obstructive Pulmonary Disease (COPD ) - terminal airway dilation and blockage from long-term smoking, infection or other chronically inhaled substances. Dangerous to the diver due to possibility of 'burst lung' and gas embolism.
 http://www.scuba-doc.com/pulprbs.html

Chronic Ulcerative Colitis (CUC) - inflammatory bowel disease sometimes requiring ostomy.
 http://www.scuba-doc.com/giprbs.html

Clearing Techniques - techniques to equalize the Eustachian tubes while descending and ascending during a dive. 
 http://www.scuba-doc.com/download/Equalizing_Techniques.zip

closed circuit scuba - apparatus designed to allow divers to re-breathe exhaled air after removal of CO2 and addition of supplemental O2. In contrast to "open circuit," closed circuit scuba is noiseless and produces no bubbles.

Cold Water Near-Drowning - drowning associated with cold water and hypothermia.
 http://www.scuba-doc.com/hypoth.htm

Congenital and Valvular Heart Disease - Abnormal passageways between the right (venous) and left (arterial) sides of the heart from birth. Heart valves that are deformed and don't open and shut properly, thereby causing heart failure.
 http://www.scuba-doc.com/hrtprb.html

Contact Irritants and Toxins - Usually nematocysts and toxins from sponges, corals and jellyfish.
 http://www.scuba-doc.com/mrnlfhz.html

Contra-indications to Diving - Listing of items that should cause a person not to dive. http://www.scuba-doc.com/fitdiv.html

Contra-indications to HBO - Listing of items that would preclude using HBO as a treatment method. http://www.scuba-doc.com/hbocont.htm

compartment - a theoretical division of the body with an arbitrarily assigned half time for nitrogen uptake and elimination. In designing decompression tables the body is divided into a finite number of compartments for purposes of making calculations, e.g., five, six or more.
 http://www.scuba-doc.com/dcsprbs.html

computer - see dive computer

Coronary Artery Disease - Abbreviation CAD. Arteriosclerosis of the arteries supplying blood to the heart. Blockage causes heart failure and 'heart attacks'.
 http://www.scuba-doc.com/hrtprb.html

Crohn's Disease - Inflammatory bowel disease associated with fistulae and sometimes requiring ostomies.
 http://www.scuba-doc.com/giprbs.html

CUC - Abbreviation for chronic ulcerative colitis
 http://www.scuba-doc.com/giprbs.html

Cutaneous DCS - skin changes associated with decompression sickness; includes cutis marmorata, edema, maculopapular rash.
 http://www.scuba-doc.com/dcsprbs.html

cutis marmorata - see above. Usually a serious form of DCS causing a mottled appearance of the skin.
 http://www.scuba-doc.com/dcsprbs.html


D

Dalton's Law - the total pressure exerted by a mixture of gases is equal to the sum of the pressures that would be exerted by each of the gases if it alone were present and occupied the total volume. http://www.scuba-doc.com/gasesprbs.html

decompression - any change from one ambient pressure to a lower ambient pressure; always results in a reduction of gas pressures within the body.
 http://www.scuba-doc.com/dcsprbs.html

decompression dive - any dive where the diver is exposed to a higher pressure than when the dive began; the decompression occurs as the diver ascends.
 http://www.scuba-doc.com/dcsprbs.html

decompression schedule - Specific decompression procedure for a given combination of depth and bottom time, normally indicated as feet/minutes.
 http://www.scuba-doc.com/dcsprbs.html

decompression stop - on ascent from a dive, a specified time spent at a specific depth, for purposes of nitrogen off-gassing; when not mandatory it is called a safety stop.
 http://www.scuba-doc.com/dcsprbs.html

DCI - see decompression illness.
 http://www.scuba-doc.com/dcsprbs.html

decompression illness - DCI; a relatively new term to encompass all bubble-related problems arising from decompression, including both decompression sickness and arterial gas embolism.
 http://www.scuba-doc.com/dcsprbs.html

DCS - see decompression sickness
 http://www.scuba-doc.com/dcsprbs.html

decompression sickness - DCS; a general term for all problems resulting from nitrogen leaving the body when ambient pressure is lowered. Can be divided into Type I (musculoskeletal and/or skin manifestations only) or the more serious Type II (neurologic, cardiac, and/or pulmonary manifestations).
 http://www.scuba-doc.com/dcsprbs.html

decompression stop - the depth at which a diver must stop on ascent for a specified period in order to eliminate inert gas before continued ascent.
 http://www.scuba-doc.com/dcsprbs.html

Deep Vein Thrombosis - clotted and blocked blood vessels in the deep venous system of the legs and pelvis.
 http://www.scuba-doc.com/hematology.htm

Dehydration - a condition where the water content of the body is reduced; caused by immersion, alcohol, medications, excessive loss of fluids from vomiting and diarrhea or decreased intake of fluids. 
 http://www.scuba-doc.com/dehyd.htm

depth - the maximum depth in fsw attained during a dive

Dermatitis - inflammation of the skin from many sources.
 http://www.scuba-doc.com/derm.html

Diabetes - Metabolic condition of decreased or absent insulin production by the pancreas.
 http://www.scuba-doc.com/endmet.html#Diabetes_and_Diving

Disabled Diving - Special diving conditions and groups that  offer the diving experience to people who have some kind of disability. http://www.scuba-doc.com/fitdiv.html

Disease Transmission Using Scuba Gear
Information about the scant risk of HIV infection from buddy breathing and rental scuba gear with links to sources about the possibility of AIDS/HIV transmission.
http://www.scuba-doc.com/AIDSrsk.htm

Disc Disease, Herniated - Extrusion of the cushion disc between the vertebrae- usually laterally placing pressure on the nerve roots of the spinal cord.
 http://www.scuba-doc.com/bone.htm

Divemaster's Quick Accident Response - Acclaimed guidelines for the rapid assessment and management of diving accidents of all types. http://www.scuba-doc.com/qkrsp.htm

Diuretics - Chemicals and medications that cause the kidneys to excrete an increased quantity of fluids.
 http://www.scuba-doc.com/drugsdiv.htm

dive computer - a small computer, carried by the diver, that constantly measures water pressure (and hence depth), and time; based on a pre-programmed algorithm, the computer calculates tissue nitrogen uptake and elimination in several theoretical compartments and provides a continuous readout of the dive profile, including: depth, elapsed time of dive, duration at current depth before decompression becomes mandatory; and a warning if the rate of ascent is too fast.

dive tables - a printed collection of dive times for specific depths, by which the diver can avoid contracting DCS. Most tables are based on Haldanian theory for nitrogen uptake and elimination.

dry suit - a water-tight garment that keeps the diver's body warm by providing insulation with a layer of gas, such as air; for diving in waters that are too cold for comfortable wet suit protection, usually below 65°F.

Dysbaric Osteonecrosis - Permanent damage done to the bones and joints by long-term diving.
 http://www.scuba-doc.com/bone.htm


E

EAN - enriched air nitrogen; nitrox.
 http://www.scuba-doc.com/nitroxlnks.html

Edentulous - without teeth; also usually with dentures.
 http://www.scuba-doc.com/dentprbs.html

Embolism, Arterial Gas - see arterial gas embolism
 http://www.scuba-doc.com/ageprbs.html

Endocrine - related to hormonal excretion of regulatory chemicals.
 http://www.scuba-doc.com/endmet.html

ENT - Ear, Nose and Throat diseases and conditions.
 http://www.scuba-doc.com/entprobs.html

Entonox - Mixture of nitrous oxide and oxygen (50-50). Dangerous to administer to divers.
 http://www.scuba-doc.com/gasesprbs.html

Epilepsy - condition of the brain associated with seizures, inimical to diving.
 http://www.scuba-doc.com/nbjprb.htm

eustachian tube - a short, muco-cartilaginous tube connecting the back of the nose to the middle ear. The anatomy of this tube is such that it tends to close naturally when ambient pressure is higher than middle ear pressure (as on descent in a dive), and tends to open naturally when ambient pressure is lower than middle ear pressure (on ascent).
http://www.scuba-doc.com/entprobs.html

External Otitis -  otitis externa. Infection of the ear canal.
 http://www.scuba-doc.com/otext.htm

first stage regulator - regulator attached to the scuba tank that lowers the tank pressure to ambient pressure + a pre-determined pressure (e.g., ambient + 140 psi).


F

Flatus - gas in the gi tract produced by the products of digestion or swallowed air, as when clearing.
 http://www.scuba-doc.com/giprbs.html

Foramen Ovale, Patent - Opening in the heart between the right and left atria that remains open in about 30 % of people, allowing passage of bubbles into the arterial circulation and symptoms of arterial gas embolism.
 http://www.scuba-doc.com/hrtprb.html

free diving - variably defined; in some usage, diving without any scuba or other equipment and synonymous with breath-hold diving; in other usage, diving with-out any attachment to the surface, and therefore includes scuba diving.
 http://www.scuba-doc.com/gasesprbs.html

fsw - feet of sea water; used to indicate either an actual depth, or just a pressure equal to that depth (e.g., in a hyperbaric chamber).


G

Gag Reflex, Overactive - the inability to retain an object in the mouth without gagging or retching.
 http://www.scuba-doc.com/dentprbs.html

gas embolism - see arterial gas embolism

gas laws - laws that predict how gases will behave with changes in pressure, temperature and volume.
http://www.scuba-doc.com/gasesprbs.html

Gastrointestinal - pertaining to the digestive tract.
 http://www.scuba-doc.com/dentprbs.html

gauge pressure - pressure exclusive of atmospheric pressure; when diving, gauge pressure is due solely to the water pressure.

Genetic - pertaining to the passage of traits from one individual to another through genes and chromosomes.

Glaucoma - abnormal condition of increased intra-ocular pressure, leading to blindness if uncorrected.
 http://www.scuba-doc.com/diveye.htm


H

half time - half the time it takes for a dissolved gas in a tissue (such as nitrogen) to equilibrate to a new pressure, or to reach full saturation at a new pressure. Theoretical tissue half times are used in designing dive tables and algorithms for dive computers.http://www.scuba-doc.com/gasesprbs.html

Haldanian - related to Haldane's theory that nitrogen is taken up and given off in exponential fashion during a dive, and that there is some safe ratio of pressure change for ascent (originally, 2:1).
http://www.scuba-doc.com/gasesprbs.html

Hazardous Marine Life - living creatures in the marine environment that are dangerous or harmful to the diver.
 http://www.scuba-doc.com/mrnlfhz.html

HBO Chambers - chambers that lower (or raise) the pressures surrounding an individual, usually using periods of 100% oxygen for purposes of treating diving and other conditions.
 http://www.scuba-doc.com/hbo.html

Hearing Loss - a hazard of diving, usually associated with rupture of round window or inner ear DCS.
 http://www.scuba-doc.com/entprobs.html

Heartburn - reflux of acid gastric juice into the lower esophagus. Also called GERD.
 http://www.scuba-doc.com/giprbs.html

heliox - mixture of helium and oxygen, used for very deep diving. http://www.scuba-doc.com/gasesprbs.html

helium - second lightest gas; does not cause problems of narcosis seen with nitrogen, and is therefore used for very deep diving. http://www.scuba-doc.com/gasesprbs.html

Henry's Law - the amount of any given gas that will dissolve in a liquid at a given temperature is a function of the partial pressure of the gas in contact with the liquid and the solubility coefficient of the gas in the liquid. http://www.scuba-doc.com/gasesprbs.html

Hematology - the study of the blood.
 http://www.scuba-doc.com/hematology.htm

hernia - a weakness of the abdominal wall through which the intestines or other intraabdominal contents protrude. Dangerous to a diver if a loop of air-containing intestine is trapped outside the abdomen.http://www.scuba-doc.com/giprbs.html

Herniated Disc Disease - see disc disease.
 http://www.scuba-doc.com/nbjprb.htm

Hernias- see abdominal hernias
http://www.scuba-doc.com/giprbs.html

high pressure nervous syndrome - convulsions or seizure-like activity arising from high gas pressure at depth, especially with helium. Abbreviation is HPNS.
 http://www.scuba-doc.com/gasesprbs.html

hookah - a surface-supplied compressed air apparatus, for use in shallow diving in calm waters. The air is delivered to one or more divers through a long hose.

hydrogen - an inert gas, and lightest of all the elements; has been used in experimental diving situations.http://www.scuba-doc.com/gasesprbs.html

hyperbaric chamber - air-tight chamber that can simulate the ambient pressure at altitude or at depth; is used for treating decompression illness. http://www.scuba-doc.com/hbo.html

hypercapnia - a higher than normal PCO2 level in the blood. Also hypercarbia. http://www.scuba-doc.com/gasesprbs.html

Hypertension - condition where the blood pressure (gauge) is above 140/90. http://www.scuba-doc.com/hrtprb.html

hyperthermia - a body temperature warmer than normal; less common in diving than hypothermia, but can occur from overheating in a wet suit.

Hyperthyroidism - condition where the thyroid gland produces too much hormone. http://www.scuba-doc.com/endmet.html

Hyperventilation - condition where an individual breathes too rapidly and has a lowered CO2, lowered Ca++ with the production of tetany; usually due to panic. http://www.scuba-doc.com/psyc.html

hypothermia - a body temperature colder than normal (37°C/98.6°F); severe problems start to manifest when body temperature reaches about 35°C (95°F).http://www.scuba-doc.com/hypoth.htm

hypoventilation - under breathing to the extent that the blood carbon dioxide level is elevated; may be manifested by carbon dioxide narcosis. http://www.scuba-doc.com/gasesprbs.html

hypoxemia - lower than normal PO2 level in the blood; insufficient oxygen in the blood. http://www.scuba-doc.com/gasesprbs.html

hypoxia - same as hypoxemia; terms are often used interchangeably. http://www.scuba-doc.com/gasesprbs.html

Hypoxia, Latent - see shallow water blackout http://www.scuba-doc.com/gasesprbs.html


I

Immersion Hypothermia - lowering of body temperature by full body immersion in cold water. See hypothermia.http://www.scuba-doc.com/hypoth.htm

Infection, HIV - infection with the human immune virus. Not necessarily a contra-indication to diving.http://www.scuba-doc.com/aaids.htm

Infection, Marine Wound - infection wit marine organisms that are particularly virulent and resistant to usual antibiotics. http://www.scuba-doc.com/aaids.htm

Inflammatory Bowel Disease - inflammations of the intestines, including CUC and Crohn's disease. http://www.scuba-doc.com/giprbs.html

Inner Ear - that portion of the ear in the petrous bone that has to do with hearing organs and balance.http://www.scuba-doc.com/entprobs.html

Intestinal Gas - see flatus.
 http://www.scuba-doc.com/giprbs.html


J


K

L

latent hypoxia - a sudden unconsciousness, from hypoxia, that occurs among some breath hold divers. Often occurs near the surface after a deeper dive. Same as "shallow water blackout."
 http://www.scuba-doc.com/gasesprbs.html

Lice, sea - description of the condition caused by the nematocysts of the thimble jellyfish. http://www.scuba-doc.com/mrnlfhz.html

Liebermeister's sign - circumscribed pallor of the tongue associated with Arterial Gas Embolism.http://www.scuba-doc.com/ageprbs.html

live aboard - a dive boat with sleeping and eating accommodations. Commercial liveaboards are usually between 50 and 130 feet long, and can carry anywhere from 10 to 30+ divers for a week or more.


M

Mal de mer - motion sickness or sea sickness. http://www.scuba-doc.com/seask.html

Marfan's Syndrome - Familial condition produced by an absent protein that causes, among other things, aortic aneurysms and pulmonary cysts. http://www.scuba-doc.com/mrfnsynd.html

Marine Associated Infections - infectious organisms living in sea water that are particularly virulent to immunosuppressed individuals. http://www.scuba-doc.com/mrnlfhz.html

Marine Life Hazards - Ocean life that offer hazards to the diver.
 http://www.scuba-doc.com/mrnlfhz.html

Masks, Prescription Dive - masks especially produced with a prescription for the individual diver.http://www.scuba-doc.com/diveye.htm

middle ear - air-containing space of the ear bordered on one side by the tympanic membrane, which is exposed to any change in ambient pressure. Air pressure in the middle ear space can only be equalized through the eustachian tube, which connects the middle ear to the back of the nose. http://www.scuba-doc.com/entprobs.html

Middle Ear Barotrauma - damage done to the middle ear due to inability to equalize the pressure differentials as a diver descends and ascends. http://www.scuba-doc.com/entprobs.html

Migraines - recurring headaches that  are triggered by certain exogenous factors such as stress, dietary indiscretions, allergens.
 http://www.scuba-doc.com/mgrns.htm

Mitral Valve Prolapse - an incompetent, floppy valve in the heart between the left atrium and ventricle.
 http://www.scuba-doc.com/hrtprb.html

mixed gas - variously defined; basically, any non-air mixture (e.g., nitrox), although some authors use the term only for mixes that contain a gas in addition to (or in place of) nitrogen (e.g., helium).

Multiple Sclerosis - Demyelinating neurological illness causing symptoms similar to DCS. http://www.scuba-doc.com/msdiv.htm


N

Nasal Congestion - swollen, blood-filled linings of the nose and sinuses, often due to allergies (rhinitis).http://www.scuba-doc.com/entprobs.html

NAUI - National Association of Underwater Instructors
 http://www.naui.org/

Near Drowning, Cold Water Immersion - see hypothermia, http://www.scuba-doc.com/hypoth.htm

nitrogen - inert gas that makes up 78% of air. Nitrogen is inert in that it does not enter into any chemical reaction in the body, but it can cause problems under pressure (see nitrogen narcosis, decompression sickness). http://www.scuba-doc.com/gasesprbs.html

narcosis - depressed mental state, anywhere from confusion or drowsiness to coma. http://www.scuba-doc.com/gasesprbs.html

nitrogen narcosis - depressed mental state from high nitrogen pressure; usually does not begin to manifest on compressed air until below 80 fsw. http://www.scuba-doc.com/gasesprbs.html

nitrox - any mixture of nitrogen and oxygen that contains less than the 78% nitrogen as found in ordinary air. http://www.scuba-doc.com/gasesprbs.html

NOAA - National Oceanic and Atmospheric Association.
 http://www.noaa.gov/

Neurologic Problems - problems of the brain and spinal cord caused by diving; neurologic difficulties adversely impacting the diver (epilepsy) http://www.scuba-doc.com/nbjprb.htm


O

OEA - Oxygen enriched air; nitrox.

open circuit scuba - apparatus used in recreational diving; exhaled air is expelled into the water as bubbles; no part is rebreathed by the diver.

otitis - inflammation or infection of any part of the ear; otitis media involves the middle ear, otitis externa the outer ear (ear canal). http://www.scuba-doc.com/entprobs.html

Otitis externa - inflammation and infection of the external auditory canal - usually due to fungus and decreased acidity of the canal. http://www.scuba-doc.com/entprobs.html

Osteonecrosis, Dysbaric - see dysbaric osteonecrosis
 http://www.scuba-doc.com/bone.htm

Overactive Gag reflex - see gag reflex
 http://www.scuba-doc.com/dentprbs.html

oxygen - O2; gas vital for all life on this planet; makes up 21% of air by volume. http://www.scuba-doc.com/gasesprbs.html

oxygen therapy - administration of any gas, for medical purpose, that contains more than 21% oxygen.http://www.scuba-doc.com/gasesprbs.html

oxygen toxicity - damage or injury from inhaling too much oxygen; can arise from either too high an oxygen concentration or oxygen pressure. The first manifestation of oxygen toxicity while diving can be seizures.
 http://www.scuba-doc.com/gasesprbs.html

oxygen window - difference between total gas pressures in arterial and venous blood; exists because oxygen is partly metabolized by the tissues, so venous oxygen pressure is lower than arterial oxygen pressure. http://www.scuba-doc.com/gasesprbs.html

oxyhemoglobin - molecule of combination between oxygen and hemoglobin responsible for the transfer of oxygen from the lungs to the tissues. http://www.scuba-doc.com/hematology.htm


P

pacemakers - electronic device that sends signals to the heart causing a rhythm change. http://www.scuba-doc.com/hrtprb.html

PADI - Professional Association of Diving Instructors http://www.padi.com/

partial pressure - pressure exerted by a single component of a gas within a gas mixture, or dissolved in a liquid. http://www.scuba-doc.com/gasesprbs.html

partial pressure, carbon dioxide - PCO2; pressure exerted by carbon dioxide in any mixture of gases, or dissolved in a liquid. http://www.scuba-doc.com/gasesprbs.html

partial pressure, nitrogen - PN2; pressure exerted by nitrogen component in any mixture of gases, or dissolved in a liquid. http://www.scuba-doc.com/gasesprbs.html

partial pressure, oxygen - PO2; pressure exerted by oxygen in any mixture of gases, or dissolved in a liquid.http://www.scuba-doc.com/gasesprbs.html

Patent foramen ovale - see foramen ovale http://www.scuba-doc.com/hrtprb.html

pneumomediastinum - abnormal collection of air in the middle part of the chest, between the two lungs (mediastinum); often a consequence of barotrauma. http://www.scuba-doc.com/ageprbs.html

pneumothorax - abnormal collection of air outside the lining of the lung, between the lung and the chest wall; often a consequence of barotrauma. http://www.scuba-doc.com/ageprbs.html

Polluted Water, Diving - special equipment and procedures for diving in polluted waters. http://www.scuba-doc.com/mrnlfhz.html

Polycythemia vera - condition of abnormal increase in production of red blood cells. http://www.scuba-doc.com/hematology.htm

Prescription Dive masks - dive masks produced especially for divers needing refractive correction.http://www.scuba-doc.com/diveye.htm

pressure - any force exerted over an area; see atmospheric pr., ambient pr. http://www.scuba-doc.com/gasesprbs.html

psi - pounds per square inch; a common measurement of air pressure. http://www.scuba-doc.com/gasesprbs.html

Pulmonary Barotrauma - rupture of the lung surface from increased pressure of ascent from depth. Usually due to closed glottis, pulmonary blebs or terminal airway disease. Causes arterial gas embolism, pneumothorax, pneumomediastinum. http://www.scuba-doc.com/pulprbs.html

Pulmonary Edema of Diving - fluid accumulation in the lungs secondary to immersion and pressure changes.http://www.scuba-doc.com/pulprbs.html

Pulmonary Decompression Sickness (Chokes) - see chokes http://www.scuba-doc.com/pulprbs.html


Q

FAQ, Frequently Asked Questions
http://scuba-doc.com/Q&A.html

QT interval,
Long
Syndrome, and is identified by specific genes that cause the abnormality. [The Q-T interval is ... Drugs Can Prolong the Q-T interval The combination ... and a prolonged Q-T interval is
http://www.scuba-doc.com/longQT.html


Quick Accident Response Page, Divemasters
Aids and butterfly bandages Q-TipsTongue depressors Disposable cups Razor blades, single edged Shaving cream Tweezers or forceps Needle nosed pliers with wire cutters (to remove
http://www.scuba-doc.com/qkrsp.htm

V/Q) mismatching in Hypothermia and Near Drowning
. As much as 75% of blood flow may circulate through hypoventilated lungs. In salt water near drowning, surfactant washout occurs, and rapid exudation of protein-
http://www.scuba-doc.com/hypoth.htm


R

recreational scuba diving - diving to prescribed limits, including a depth no greater than 130 fsw, using only compressed air, and never requiring a decompression stop; abbreviated RSD.

Refractive Correction -lens configuration needed to correct a defect in a divers vision. http://www.scuba-doc.com/diveye.htm

regulator - in scuba, any device which changes air pressure from one level to a lower level. See first and second stage regulator.

repetitive dive - any dive done within a certain time frame after a previous dive; variable definition exists as to what time frame constitutes "repetitive." With some tables any dive within 12 hours of a previous dive is considered repetitive; when using a computer, any dive whose profile is affected by a previous dive is considered repetitive. http://www.scuba-doc.com/gasesprbs.html

residual nitrogen - nitrogen that remains dissolved in a diver's tissues after surfacing from a dive.http://www.scuba-doc.com/gasesprbs.html

residual nitrogen time - the time it would take to off-gas any extra nitrogen remaining after a dive; in dive tables, RNT is designated by a letter A through Z. Residual nitrogen time is always taken into consideration in determining the safe duration for any repetitive dive. http://www.scuba-doc.com/gasesprbs.html

reverse squeeze - pain or discomfort in enclosed space (e.g., sinuses, middle ear, inside face mask) on ascent from a dive.
 http://www.scuba-doc.com/entprobs.html

S

safety stop - on ascent from a dive, a specified time spent at a specific depth, for purposes of nitrogen off-gassing; by definition it is not mandatory for safe ascent from the dive. Compare with decompression stop.

saturation - the degree to which a gas is dissolved in the blood or tissues; full saturation occurs when the pressure of gas dissolved in the blood or tissues is the same as the ambient (surrounding) pressure of that gas. http://www.scuba-doc.com/gasesprbs.html

saturation diving - diving performed after the body is fully saturated with nitrogen; to become fully saturated the diver must stay under water for a much longer period than is allowed in recreational scuba diving tables. http://www.scuba-doc.com/gasesprbs.html

scuba - self-contained underwater breathing apparatus.

sea level - the level of the world's oceans; all oceans are at sea level.

Sea Lice or Seabather's Eruption - dermatitis secondary to nematocysts of the thimble jellyfish.http://www.scuba-doc.com/mrnlfhz.html

Seasickness - motion sickness or mal de mer http://www.scuba-doc.com/seask.html

second stage regulator - the regulator that follows, in line, the first stage regulator, and delivers compressed air to the diver.

shallow water blackout - a sudden unconsciousness, from hypoxia, that occurs among some breath hold divers. Often occurs near the surface after a deeper dive, hence "shallow water." Same as 'latent hypoxia'. http://www.scuba-doc.com/gasesprbs.html

Sickle Cell Illness - inherited illness in which deformed red blood cells cause blood vessel blockage. Low oxygen precipitates a crisis. http://www.scuba-doc.com/hematology.htm

single dive - Any dive conducted at least 12 hours after a previous dive.

sinuses - air spaces within the skull that are in contact with ambient pressure through openings into the back of the nasal passages. http://www.scuba-doc.com/entprobs.html

sinusitis - inflammation or infection of the sinuses in the head. http://www.scuba-doc.com/entprobs.html

Sjogren's Syndrome - An arthritic condition associated with drying out and loss of salivary gland activity, tear duct activity and adverse to diving. http://www.scuba-doc.com/sjogren.htm

skin diving - another term for breath-hold diving; diving without the use of scuba equipment. http://www.scuba-doc.com/gasesprbs.html

skip breathing - this simply means holding the breath after breathing in and/or holding the breath for a variable period of time after breathing out. This is done subconsciously or on purpose in order to "conserve air" - either to stop using too much air or to try to prolong a dive. It is dangerous for several reasons. It causes a subtle buildup of CO2 with all of the attendant risks [see our web pages about this at http://snipurl.com/h2l2 ]. In addition, it imposes the risk of pulmonary barotrauma from ascending with the glottis closed, even a few feet. There are several web sites that discuss breathing control in terms of learning buoyancy control - but managing breathing for this is entirely different and does not entail 'holding the breath' but increasing and decreasing volumes. See http://snipurl.com/h2le .

Spina bifida - congenital anomaly of the spinal cord; often associated with paraplegia, bowel and bladder dysfunction http://www.scuba-doc.com/nbjprb.htm

Sprue - abnormal absorption of the GI tract; associated with cerebral calcifications and seizures. Also called coeliac disease. http://www.scuba-doc.com/giprbs.html

squeeze - pain or discomfort in an enclosed space (sinuses, middle ears, inside a face mask) caused by shrinkage of that space; occurs on descent. See reverse squeeze.http://www.scuba-doc.com/entprobs.html

Sunburn - pathological damage to the skin from the ultraviolet rays of the sun. http://www.scuba-doc.com/derm.html

surface interval - length of time on the surface, usually out of the water, between two consecutive dives.

surface-supplied compressed air diving - diving with the air continuously supplied by a compressor on the surface; can be used for both sport and professional diving. "Hookah"

supersaturation - an unstable situation where the pressure of a gas dissolved in the blood or tissues is higher than the ambient pressure of that gas. Supersaturation is always present to some degree with every decompression.

Swimmer's Itch - pruritic condition from diving in cercaria infested waters. http://www.scuba-doc.com/derm.html


T

Taravana - Native word used to describe the decompression condition that develops with frequent, deep breath-hold dives with short surface intervals. http://www.scuba-doc.com/taravana.html

TEED Classification - a method to classify the degree of damage done to the tympanic membranes and middle ear from barotrauma. Named after R W Teed who wrote in many otological journals  describing the aetiology, clinical findings and pathology of middle ear barotrauma. (Thanks to Carl Edmonds for this information!)http://www.scuba-doc.com/entprobs.html

thermocline - intersection between two layers of water of that are of decidedly different temperatures; usually the colder layer is deeper. A diver can easily feel a thermocline.

TIA - (Transient ischemic attacks) neurological condition of decreased consciousness and paralysis due to small emboli going to the cerebral circulation. Also called  'Little Strokes'. http://www.scuba-doc.com/nbjprb.htm

tinnitus - ringing sound heard by some divers after barotrauma to the inner ear. Sometimes caused by perilymph fistula and occasionally needs surgical repair.
 http://www.scuba-doc.com/entprobs.html

tissue - a part of the body characterized by specific characteristics, such as muscle, bone, or cartilage. The term is also used to refer to any part of the body with a specific half time for loading and unloading nitrogen; in this latter context a tissue may be contiguous or non-contiguous, or even a theoretical compartment.

TMJ Syndrome - Jaw and ear pain from clamping the teeth around a regulator mouthpiece. http://www.scuba-doc.com/dentprbs.html

Toxicity, O2 - the condition caused by oxygen at depth (increased pressure); usually ends in convulsions, and, drowning if under water. http://www.scuba-doc.com/gasesprbs.html

Toxicity, Pulmonary Oxygen - Condition of the lungs caused by oxygen given at increased pressure.http://www.scuba-doc.com/pulprbs.html

trimix - mixture of helium, nitrogen and oxygen, used for very deep diving.

tympanic membrane - the thin ear drum between the outer ear and the middle ear, visible to the examiner with an otoscope. http://www.scuba-doc.com/entprobs.html


U

Underwater Blast Injuries
Minor explosions have caused blast injury & death during underwater electric cutting & ... same distance an underwater blast is more ... waves from an underwater explosion combine with
http://www.scuba-doc.com/uwblast.html




V

Vein Thrombosis, Anticoagulation - See Deep vein thronbosis
 http://www.scuba-doc.com/hematology.htm

Vera, Polycythemia - Pathological condition whereby the bone marrow produces too many cells.http://www.scuba-doc.com/hematology.htm

Vertigo - Dizzy, unbalanced feeling often caused by diving problems with the inner ear.
 http://www.scuba-doc.com/vert.htm


W

Water, Diving in Polluted - http://www.scuba-doc.com/polwater.html

Water, Problems With Moving - http://www.scuba-doc.com/divcurr.htm

Water, Hypothermia and Cold Water Near Drowning - http://www.scuba-doc.com/hypoth.htm

water pressure - force per unit area exerted by the weight of water; each 33 feet of sea water exerts a pressure equivalent to one atmosphere, or 14.7 psi.

wet suit - any suit that provides thermal protection in or under water by trapping a layer of water between the diver's skin and the suit; see dry suit.


X

Histiocytosis X or Eosinophilic granuloma, pulmonary
X as a cause of pulmonary barotrauma in scuba ... in 30%, and progression in 30%. Scuba diving is contraindicated. X-ray: CXR: On CXR there is usually diffuse reticulonodularity (3
http://www.scuba-doc.com/histx.html




Y
Young divers


Z




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